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user_mp555d
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10/07/2026 8:48 PM

Signal levels out of spec on SB8200 — need line check

My customer-owned Arris SB8200 shows signal levels outside DOCSIS spec, as of Oct 7, 2026:

  • Downstream power: +9.4 to +12.7 dBmV. 31 of 32 channels are above +10 dBmV.
  • Upstream power: 51 to 53 dBmV on all 4 channels.
  • Uncorrectable errors: tens of thousands per downstream channel.
  • SNR: 42 dB or better, and all channels are locked.

Both power levels point to a line or tap problem rather than the modem. Could a support agent check my line and set up a technician visit if needed? I'm happy to send account details by direct message.

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8 hours ago

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XfinityCliff

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8 hours ago

Thanks for sharing the detailed readings here on our Xfinity Community forums @user_mp555d!

While the downstream levels are running somewhat high, they're still within the documented operating range. The upstream levels are also elevated and worth taking a closer look at, while the SNR appears healthy.

The uncorrectable errors are another reason we'd want to review the connection, although these readings by themselves don't identify exactly where an issue may be occurring.

Please send us a direct message with your full name and complete service address, and we'll be happy to investigate further.

How to Send Us a Direct Message*:
(*Note: Never send a direct message to us unless requested by us.)

  1. Click "Sign In" if necessary.
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  3. Click the "New message" (pencil and paper) icon.
  4. In the "To:" line, type "Xfinity Support".
  5. As you type, a drop-down list will appear. Select "Xfinity Support" from that list.
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  7. Type your message in the text area near the bottom of the window.
  8. Press Enter to send it.

Click Here For an example of how to send us a Direct Message.

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